The following U.S. patents are representative of the prior art: U.S. Pat. Nos. 2,431,612; 3,237,516; 2,821,882; 3,329,029; 2,923,503; 3,437,410; 2,940,358; 3,476,478.
While the majority of the patents listed above are directed to the capability of changing magnification in an optical system, none of the patents is believed anticipatory to the arrangement set forth herein for maintaining a constant document plane location and image plane location without using auxiliary lens elements and further using common reference edges on both planes for different size documents.